Whirl and Stall Flutter Simulation Using CFD

This paper presents recent research on numerical methods for whirl and stall flutter using computational fluid dynamics. The method involves coupling of the HMB3 CFD solver of the University of Glasgow and a NASTRAN derived structural model. Based upon a literature survey, a significant amount of research has been conducted on the numerical investigation of tiltrotors, with a focus on the XV-15 and V-22 aircraft. Within this paper, the coupling procedure is presented along with a steady CFD computation to highlight the accuracy of the high-fidelity method. In addition to this, a simple method is used to investigate the whirl flutter boundary of a standard propeller and the XV-15 blade

Translation, Criticism, and/or Politics: Assessing and Contextualizing Ezra Pound\u27s Homage to Sextus Propertius

My thesis attempts to address several of the major issues surrounding Ezra Pound\u27s 1919 poem Homage to Sextus Propertius, a notoriously unfaithful translation or adaptation of selected lyrics written by the eponymous Latin poet. I begin by situating Homage and its publication within the context of Pound\u27s life and milieu, focusing especially on the early discourse about how the poem fits into the Pound corpus. From here I turn to the question of what function translation--broadly defined--serves in the poem, as a bridge between literary periods and a mode of both criticism and original expression. Ultimately, I offer a reading of the poem that historicizes it as a product, in key ways, of the wartime environment in which it was written, and try to evaluate it as a major turning point in Pound\u27s career

Senior Theses: Department of Physical Sciences

1992 Senior Theses from the Department of Physical Science at Morehead State University. The Abundance, Diversity, and Stratigraphy of the Upper Crab Orchard Formation, Lewis County, Kentucky by Patrick M. Higgins. The Modification of Flemion for Use in a Solid Electrolyte Battery by Timothy Howard. Simple Analog Computers by Leah Carol Ross

Investigation of propeller stall flutter

Propeller flutter can manifest in a variety of ways. This includes classical bending-torsion flutter, stall flutter and whirl flutter. Classical bending-torsion flutter for propeller blades is driven by the coupling, and excitement, of selected modes of motion. Such flutter problems are often a result of structural coupling and in the linear aerodynamic regime. As a result, low-fidelity, fast calculations can be used to determine boundaries and mitigate the effects via changes in the structural design. Whirl flutter is the most complex and involves the coupling of the aircraft wing modes of motion to the gyroscopic and aerodynamic effects of the propeller. This phenomenon can be highly non-linear due to both the structure and flow-field, and any mitigation involves sophisticated modelling efforts with respect to the airframe. Propeller stall flutter is less complex in terms of the structure, however, involves the highly non-linear aerodynamics associated with detached flow. This phenomena, like classical flutter, is driven by the propeller design and conditions, but due to its nature, the stall flutter boundary significantly reduces the overall flutter boundary of a propeller. Hence, the understanding of this limitation must be known to ensure safe operation. The development of modern propeller blades utilising high sweep/taper with thin aerofoil sections can result in a change in the flutter boundary. In addition to this, propellers are coming back into focus due to the development of electrically driven Vertical Take-off/Landing (eVTOL) vehicles and, due to the nature of such a vehicle design, the propellers are being pushed into significantly different operating conditions. This motivation, coupled with the increased computational power available in the modern era, requires the need to reassess what is required to understand the stall flutter boundary associated with a modern, in-service, propeller blade. To this end, a numerical investigation using Computational Fluid Dynamics (CFD) and Computational Structural Dynamics (CSD) was conducted on the Commander propeller blade of Dowty Propellers. This blade was selected from the list of experimentally investigated blades due to the availability of geometry, structural data and applicability in real life applications. A validation procedure was conducted to assess the effects of the computational setup. This included the effects of turbulence, structural modelling and implementation, with a validated process found whilst using Scale-Adaptive-Simulation (SAS) with interpolated structural modes. An attempt was made to extract aerodynamic damping data of the stall flutter phenomenon via the development of a method from the aeroelastic simulations. Such values give an indication of the stability, with links made to typical two-dimensional modelling. The thesis ends on the parametric study of the validated Commander simulation. This was conducted in order to gain greater detail on the effects of key structural and aerodynamic parameters on the blade stall flutter response. The key outcome from this investigation is the need for scale-resolving methods in propeller stall flutter investigations. This study utilises a hybrid RANS/LES model to capture the key detached flow content. This detached flow content results in significant pressure fluctuations, not observed in traditional statistical models, which drive the aeroelastic deformations. In addition, the requirement for a well validated structural model is highlighted including the setup of the structural solver for which an interpolated modal response method is used. It is also found from this investigation that there is a need for a modern experimental test case focusing on propeller stall flutter. The last comprehensive study was conducted in the 1980’s and, with improvements in experimental techniques, greater understanding and data can now be extracted. This new data can be used to validate modern CFD efforts. The novelty of this work lies within the derivation of a method for the extraction of the aerodynamic damping data from three-dimensional simulations. This had previously not be done before and the extracted results correlated with equivalent two-dimensional aerodynamic damping data. Additionally, the development and application of three-dimensional Navier-Stokes based CFD, with a coupled structural model, had not been conducted on propeller stall flutter

A Time-Marching Aeroelastic Method Applied to Propeller Flutter

A time-marching aeroelastic method developed for the study of propeller flutter is presented and validated. Propeller flutter can take many forms with stall, whirl and classical flutter being the primary responses. These types of flutter require accurate capture of the non-linear aerodynamics associated with propeller blades. Stall flutter in particular, due to the highly detached nature of the flow, needs detailed unsteady flow modelling. With the development of modern propeller designs potentially adjusting the flutter boundary and the development of faster computing power, CFD is required to ensure accurate capture of aerodynamics. This paper focuses on the validation of the aeroelastic method using the Commander propeller blade

Numerical investigation of a two-bladed propeller inflow at yaw

The development of faster computing power and nonintrusive experimental techniques has allowed for the advancement in computational fluid dynamics (CFD) validation and the greater understanding of aerodynamic conditions previously deemed too extreme to accurately measure. To this end, a numerical study is conducted that focuses on a propeller at yaw. Current low-order methods are reliant upon an accurate inflow profile to determine overall blade loading patterns. To improve such methods, CFD can be used to determine an initial inflow profile from which to conduct additional lower-order calculations. Therefore, to ensure that CFD is able to accurately capture yawed inflow profiles, a validation study is conducted that compares numerical simulations against experiments. Good agreement is found between the two methods, and subsequently the azimuthal variation in skin friction and induced angle of attack, as a result of the yawed conditions, is analyzed

Evidence for a core-shell structure of hydrothermal carbon

Hydrothermal carbonisation (HTC) has been demonstrated to be a sustainable thermochemical process, capable of producing functionalised carbon materials for a wide range of applications. In order to better apply such materials, the local chemistry and reaction pathways governing hydrothermal carbon growth must be understood. We report the use of scanning transmission X-ray microscopy (STXM) to observe chemical changes in the functionality of carbon between the interface and bulk regions of HTC. Spatially-resolved, element-specific X-ray photo-absorption spectra show the presence of differing local carbon chemistry between bulk “core” and interface “shell” regions of a glucose-derived hydrothermal carbon spherule. STXM provides direct evidence to suggest that mechanistic pathways differ between the core and shell of the hydrothermal carbon. In the shell region, at the water-carbon interface, more aldehyde and/or carboxylic species are suspected to provide a reactive interface for bridging reactions to occur with local furan-based monomers. In contrast, condensation reactions appear to dominate in the core, removing aryl-linking units between polyfuranic domains. The application of STXM to HTC presents opportunities for a more comprehensive understanding of the spatial distribution of carbon species within hydrothermal carbon, especially at the solvent-carbon interface